1. Field
The present invention relates generally to communication systems, and more particularly, to systems and methods for uplink rate selection in the presence of multiple transport channels in a wireless communication system.
2. Background
An exemplary wireless telecommunications system may be designed in accordance with the 3GPP standard, Release 99, which is known to those of skill in the art and is hereby incorporated by reference. In this system, a base station controller is coupled to a plurality of base transceiver stations, or base stations. There may be many base stations that are coupled to the base station controller. The base station controller is typically coupled to the base stations through a network that is typically referred to as the backhaul network.
Each base station is capable of communicating with a plurality of mobile stations that are within a coverage area associated with the base station. Again, there may be many mobile stations in the base station's coverage area that are communicating with the base station. The mobile station communicates with the base station via a wireless link. The wireless link includes a set of channels for communicating data from the base station to the mobile station, as well as a set of channels for communicating data from the mobile station to the base station. The first set of channels (from base station to mobile station) are referred to as the forward link. The second set of channels (from mobile station to base station) are referred to as the reverse link.
In this system, when the mobile station has data that it needs to transmit to the base station, a request is transmitted from the mobile station to the base station. This request is a request for permission to transmit the mobile station's data to the base station. After the base station receives the request, it may issue a grant to the mobile station in response to the request. The grant allows the mobile station to transmit data to the base station at up to a specified maximum data rate for an allotted interval.
When the grant is received by the mobile station, the mobile station determines an appropriate rate at which to transmit its data, and then transmits the data over a dedicated data channel at the selected rate during the allotted interval. The mobile station selects a data rate at which to transmit data on the dedicated data channel based in large part on its power constraints. For example, in this system, the mobile station has a maximum power (e.g., 125 milliwatts) with which it can transmit its data, so a data rate is selected that is not expected to cause the mobile station to exceed its maximum power level. In this system, the mobile station's history (with respect to the amount of power required to transmit at a given data rate) is viewed to determine the maximum allowable data rate corresponding to a power level that is below the maximum level.
This simple method of selecting a data rate, however, accounts for only a single channel (the dedicated data channel) and does not provide an acceptable methodology for rate selection if the mobile station will be transmitting data over multiple channels. It would therefore be desirable to provide systems and methods for selecting data rates in the presence of multiple channels.